Absolutely not, and in fact, I'd caution you to not use true magic items as your go-to solution for an icon relationship. It's okay to use them occasionally, but as page 191 of the core rulebook explains, the game functions better when your players are hungry for magic items rather than when they are satiated.
We prefer it when characters are hungry for more magic rather than feeling like they are close to full. We suggest that the optimal number of magic items for a character is somewhere between half the character’s level and the character’s level. If there’s 50% to 75% chance that a character gains a new magic item over the course of a full level, that’s good by us.
That being said, there's nothing wrong with giving a player a true magic item as a manifestation of their icon benefit. I especially like doing so for 5's, rather than 6's, because it gives you cause to make the character earn the item as the result of an accomplishment, rather than "hey, I like you, here's a Cool Sword".
The game recommends a player receive a true magic item at most once over the course of a level, which is about once every twelve to sixteen fights, give or take (see page 189 of the core rulebook). There's room for a solid amount of adventures there. Characters will find ways to perform feats of heroism, take down major foes, and make bargains with powerful entities. Icon benefit or no, there's definitely room to reward these acts with a true magic item.